#include <stdio.h>
void f(int * * a, int * b)
{
  * a = b; /* a points to where b points to */
}

int main(int argc, char * argv[])
{
  int x = 100;
  int * y;
  f(& y, & x);
  * y = 200;
  printf("x's value is %d\n", x);
  return 0;
}
